There are a number of existing methods for measuring the soil hydrologic properties such as field capacity (FC), saturation (Sat), permanent wilting point (PWP), and plant available water (PAW). One method is to directly measure these quantities in the physical laboratory using a tension table. Meanwhile, other methods estimate these hydrologic properties, such as pedotransfer functions (PTFs), compaction, electrical conductivity, salinity, gravel content etc., which evaluate several soil properties including: sand, clay, and soil organic matter (SOM), among others; which derive these output quantities using associated mathematical functions. PTFs, also referred to as PTF models, vary by regional design and may include other model inputs with varying degrees of sensitivity.
When hydrologic properties are estimated using PTFs the model inputs are typically acquired through laboratory analysis via pipette, using sedimentation methods, or inferred from infield mapping of soil electrical conductivity. These processes are costly with respect to human labor and laboratory footprint. As a result, PTFs are not used in commercial agronomic practice due to the high cost of analysis. Particularly, using an infield instrument that can spatially map electrical conductivity involves pulling along an electromagnetic instrument over the field and collecting the electrical conductivity of the soil underneath the instrument; this method is expensive, and does not scale well to a large service offering covering a large number of acres.